Project Summary. This research takes an intergenerational lifespan perspective to the development of trait psychological functioning. There are well-documented connections between Conscientiousness and Neuroticism and aging- related outcomes: Individuals who score higher in Conscientiousness and lower in Neuroticism have lower risk of Alzheimer?s disease and greater longevity. The association between these traits and better health begins early in life and persist across the lifespan. Early interventions to promote healthier trait development will lead to broad improvements in health and well-being and ultimately better aging outcomes. Yet, little is known about the early environmental origins of these traits that would be promising targets of intervention. Likewise, relatively little is known about how biological factors contribute to trait development across the lifespan. The present research brings together three established longitudinal studies of well-characterized cohorts to identify prenatal and childhood environmental factors (broadly construed) that contribute to the development of personality, the biological mediators of these associations, and the dynamics between prenatal/childhood factors and personality on a consequential health outcome ? the development and aging of cognitive functioning across the lifespan. Together, these three cohorts cover conception through older adulthood: The Longitudinal Study of Australian Children covers pregnancy through age 12, the Avon Longitudinal Study of Parents and Children covers pregnancy through young adulthood, and the Healthy Aging in Neighborhoods of Diversity across the Life Span covers middle through older adulthood. This research addresses three specific aims: (1) To identify maternal prenatal behavioral and clinical antecedents of temperament and personality traits and to test biological markers as one mechanism through which prenatal factors contribute to trait psychological functioning, (2) To identify childhood neighborhood antecedents of trait psychological functioning in childhood, adolescence, and adulthood and to test biological markers as one mechanism through which neighborhood factors contribute to trait psychological functioning, and (3) To test whether personality traits mediate and/or moderate the relation between the prenatal/childhood environment and cognitive functioning across the lifespan. The outcomes of this research will lead to new knowledge on the origins of the traits most relevant for healthy aging and suggest promising new targets for intervention.